Digging deep excavations, such as cross-country ditches, necessitates that a considerable amount of material is removed from the ground in order to provide a ditch bottom which is constructed at a specific elevation, or grade. Construction of deep ditches and other excavations usually requires a ladder type digging apparatus, such as shown, for example, in my previous patent, U.S. Pat. No. 4,755,001, and in my co-pending patent application Ser. No. 08/245,942 filed May 19, 1994, entitled "WIDE TRENCHER WITH PLURALITY OF CHAIN TYPE DIGGERS". My previous patent, U.S. Pat. No. 4,755,001, and my co-pending patent application each disclose an excavating machine having a ladder type digging apparatus that translocates excavated material from the ditch by means of the lower run of the digging member, up through a throat, and then along a lateral conveyor to a location spaced from the excavating machine. The dissipation of the enormous digging force applied to the lower run of the ladder type digging apparatus results in very high temperatures being generated on the lower surface of the boom, especially the marginal free depending end near the tail wheel of the boom, because of the forces involved as the lower run of the digging member engages and excavates the ground. The generated high temperatures accelerate wear between the co-acting parts of the digging apparatus, and this brings about costly repairs which usually also results in expensive downtime.
In the past, wear plates are arranged on the boom to accept wear caused by the friction associated with the lower run of the endless digging chains of the digging apparatus. The wear plates are usually installed by direct fixation by welding the plates directly to the underside of the boom where the heat generated therein is rapidly transferred into all of the moving parts associated with the plates. This generated heat creates premature malfunction of the boom parts due to the high operating temperatures, which accelerates the wear rate, and thereby many causes many difficult repair problems. Further, replacement of the fixed wear plates is difficult to effect in the field, and is a time consuming, expensive, and difficult task.
The present invention overcomes many of the above problems by the provision of a fluid cooled boom in combination with improvements in wear plates which are designed to be inexpensively replaced in the field. Another important feature of the invention is the arrangement of the wear plates to readily dissipate heat to the atmosphere rather than transfer the heat directly into the boom parts, including the lower run of the digging member. Thus, the invention dissipates heat into the atmosphere while at the same time heat that is transferred from the improved wear plates into the bottom of the boom is rapidly removed from a high temperature region to relatively cooler parts of the boom where it is dissipated by convection and radiation into the atmosphere. Method and apparatus by which these desirable and novel achievements are realized are the subject of the present invention.